As the interest in information displays increases and requirements for using portably information devices increase, a research about flat panel displays replacing the existing cathode ray tubes has been increasingly conducted and more products have been commercialized. For example, a liquid crystal display, which is a type of flat panel display devices, has been developed. The liquid crystal display may display an image using, e.g., optical anisotropy of a liquid crystal, and may have high resolution, color display, and image quality. The liquid crystal display may be used, e.g., for notebooks and desktop monitors. The liquid crystal display may also have a touch screen function that allows a user's commands to be inputted by selection on the screen.